/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.evaluation;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.constant.ClassConstant;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.*;
import proguard.classfile.visitor.*;
import proguard.evaluation.*;
import proguard.evaluation.value.*;
import proguard.optimize.OptimizationInfoClassFilter;
import proguard.optimize.info.SimpleEnumMarker;

/**
 * This ClassVisitor marks enums that can't be simplified due to the way they are used in the classes that it visits.
 *
 * @see SimpleEnumMarker
 * @author Eric Lafortune
 */
public class SimpleEnumUseChecker extends SimplifiedVisitor
    implements ClassVisitor, MemberVisitor, AttributeVisitor, InstructionVisitor, ConstantVisitor, ParameterVisitor {
    // *
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = System.getProperty("enum") != null;
    //*/

    private final PartialEvaluator partialEvaluator;
    private final MemberVisitor methodCodeChecker = new AllAttributeVisitor(this);
    private final ConstantVisitor invokedMethodChecker = new ReferencedMemberVisitor(this);
    private final ConstantVisitor parameterChecker = new ReferencedMemberVisitor(new AllParameterVisitor(false, this));
    private final ClassVisitor complexEnumMarker = new OptimizationInfoClassFilter(new SimpleEnumMarker(false));
    private final ReferencedClassVisitor referencedComplexEnumMarker = new ReferencedClassVisitor(complexEnumMarker);

    // Fields acting as parameters and return values for the visitor methods.
    private int invocationOffset;

    /**
     * Creates a new SimpleEnumUseSimplifier.
     */
    public SimpleEnumUseChecker() {
        this(new PartialEvaluator(new TypedReferenceValueFactory()));
    }

    /**
     * Creates a new SimpleEnumUseChecker.
     * 
     * @param partialEvaluator the partial evaluator that will execute the code and provide information about the
     *        results.
     */
    public SimpleEnumUseChecker(PartialEvaluator partialEvaluator) {
        this.partialEvaluator = partialEvaluator;
    }

    // Implementations for ClassVisitor.

    public void visitProgramClass(ProgramClass programClass) {
        if ((programClass.getAccessFlags() & ClassConstants.ACC_ANNOTATION) != 0) {
            // Unmark the simple enum classes in annotations.
            programClass.methodsAccept(referencedComplexEnumMarker);
        } else {
            // Unmark the simple enum classes that are used in a complex way.
            programClass.methodsAccept(methodCodeChecker);
        }
    }

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {
        // Evaluate the method.
        partialEvaluator.visitCodeAttribute(clazz, method, codeAttribute);

        int codeLength = codeAttribute.u4codeLength;

        // Check all traced instructions.
        for (int offset = 0; offset < codeLength; offset++) {
            if (partialEvaluator.isTraced(offset)) {
                Instruction instruction = InstructionFactory.create(codeAttribute.code, offset);

                instruction.accept(clazz, method, codeAttribute, offset, this);

                // Check generalized stacks and variables at branch targets.
                if (partialEvaluator.isBranchOrExceptionTarget(offset)) {
                    checkMixedStackEntriesBefore(offset);

                    checkMixedVariablesBefore(offset);
                }
            }
        }
    }

    // Implementations for InstructionVisitor.

    public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        SimpleInstruction simpleInstruction) {
        switch (simpleInstruction.opcode) {
            case InstructionConstants.OP_AASTORE: {
                // Check if the instruction is storing a simple enum in a
                // more general array.
                if (!isPoppingSimpleEnumType(offset, 2)) {
                    if (DEBUG) {
                        if (isPoppingSimpleEnumType(offset)) {
                            System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] stores enum ["
                                + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                                + "] in more general array ["
                                + partialEvaluator.getStackBefore(offset).getTop(2).referenceValue().getType() + "]");
                        }
                    }

                    markPoppedComplexEnumType(offset);
                }
                break;
            }
            case InstructionConstants.OP_ARETURN: {
                // Check if the instruction is returning a simple enum as a
                // more general type.
                if (!isReturningSimpleEnumType(clazz, method)) {
                    if (DEBUG) {
                        if (isPoppingSimpleEnumType(offset)) {
                            System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] returns enum ["
                                + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                                + "] as more general type");
                        }
                    }

                    markPoppedComplexEnumType(offset);
                }
                break;
            }
            case InstructionConstants.OP_MONITORENTER:
            case InstructionConstants.OP_MONITOREXIT: {
                // Make sure the popped type is not a simple enum type.
                if (DEBUG) {
                    if (isPoppingSimpleEnumType(offset)) {
                        System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                            + method.getDescriptor(clazz) + "] uses enum ["
                            + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                            + "] as monitor");
                    }
                }

                markPoppedComplexEnumType(offset);

                break;
            }
        }
    }

    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        VariableInstruction variableInstruction) {}

    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        ConstantInstruction constantInstruction) {
        switch (constantInstruction.opcode) {
            case InstructionConstants.OP_PUTSTATIC:
            case InstructionConstants.OP_PUTFIELD: {
                // Check if the instruction is generalizing a simple enum to a
                // different type.
                invocationOffset = offset;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, parameterChecker);
                break;
            }
            case InstructionConstants.OP_INVOKEVIRTUAL: {
                // Check if the instruction is calling a simple enum.
                String invokedMethodName = clazz.getRefName(constantInstruction.constantIndex);
                String invokedMethodType = clazz.getRefType(constantInstruction.constantIndex);
                int stackEntryIndex = ClassUtil.internalMethodParameterSize(invokedMethodType);
                if (isPoppingSimpleEnumType(offset, stackEntryIndex)
                    && !isSupportedMethod(invokedMethodName, invokedMethodType)) {
                    if (DEBUG) {
                        System.out
                            .println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] calls [" + partialEvaluator.getStackBefore(offset)
                                    .getTop(stackEntryIndex).referenceValue().getType()
                                + "." + invokedMethodName + "]");
                    }

                    markPoppedComplexEnumType(offset, stackEntryIndex);
                }

                // Check if any of the parameters is generalizing a simple
                // enum to a different type.
                invocationOffset = offset;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, parameterChecker);
                break;
            }
            case InstructionConstants.OP_INVOKESPECIAL:
            case InstructionConstants.OP_INVOKESTATIC:
            case InstructionConstants.OP_INVOKEINTERFACE: {
                // Check if it is calling a method that we can't simplify.
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, invokedMethodChecker);

                // Check if any of the parameters is generalizing a simple
                // enum to a different type.
                invocationOffset = offset;
                clazz.constantPoolEntryAccept(constantInstruction.constantIndex, parameterChecker);
                break;
            }
            case InstructionConstants.OP_CHECKCAST:
            case InstructionConstants.OP_INSTANCEOF: {
                // Check if the instruction is popping a different type.
                if (!isPoppingExpectedType(offset, clazz, constantInstruction.constantIndex)) {
                    if (DEBUG) {
                        if (isPoppingSimpleEnumType(offset)) {
                            System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] is casting or checking ["
                                + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                                + "] as [" + clazz.getClassName(constantInstruction.constantIndex) + "]");
                        }
                    }

                    // Make sure the popped type is not a simple enum type.
                    markPoppedComplexEnumType(offset);

                    // Make sure the checked type is not a simple enum type.
                    // Casts in values() and valueOf(String) are ok.
                    if (constantInstruction.opcode != InstructionConstants.OP_CHECKCAST || !isSimpleEnum(clazz)
                        || (method.getAccessFlags() & ClassConstants.ACC_STATIC) == 0
                        || !isMethodSkippedForCheckcast(method.getName(clazz), method.getDescriptor(clazz))) {
                        if (DEBUG) {
                            if (isSimpleEnum(((ClassConstant)((ProgramClass)clazz)
                                .getConstant(constantInstruction.constantIndex)).referencedClass)) {
                                System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "."
                                    + method.getName(clazz) + method.getDescriptor(clazz) + "] is casting or checking ["
                                    + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                                    + "] as [" + clazz.getClassName(constantInstruction.constantIndex) + "]");
                            }
                        }

                        markConstantComplexEnumType(clazz, constantInstruction.constantIndex);
                    }
                }
                break;
            }
        }
    }

    public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        BranchInstruction branchInstruction) {
        switch (branchInstruction.opcode) {
            case InstructionConstants.OP_IFACMPEQ:
            case InstructionConstants.OP_IFACMPNE: {
                // Check if the instruction is comparing different types.
                if (!isPoppingIdenticalTypes(offset, 0, 1)) {
                    if (DEBUG) {
                        if (isPoppingSimpleEnumType(offset, 0)) {
                            System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] compares ["
                                + partialEvaluator.getStackBefore(offset).getTop(0).referenceValue().getType()
                                + "] to plain type");
                        }

                        if (isPoppingSimpleEnumType(offset, 1)) {
                            System.out.println("SimpleEnumUseChecker: [" + clazz.getName() + "." + method.getName(clazz)
                                + method.getDescriptor(clazz) + "] compares ["
                                + partialEvaluator.getStackBefore(offset).getTop(1).referenceValue().getType()
                                + "] to plain type");
                        }
                    }

                    // Make sure the first popped type is not a simple enum type.
                    markPoppedComplexEnumType(offset, 0);

                    // Make sure the second popped type is not a simple enum type.
                    markPoppedComplexEnumType(offset, 1);
                }
                break;
            }
        }
    }

    public void visitAnySwitchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        SwitchInstruction switchInstruction) {}

    // Implementations for MemberVisitor.

    public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod) {}

    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod) {
        if (isSimpleEnum(programClass)
            && isUnsupportedMethod(programMethod.getName(programClass), programMethod.getDescriptor(programClass))) {
            if (DEBUG) {
                System.out.println("SimpleEnumUseChecker: invocation of [" + programClass.getName() + "."
                    + programMethod.getName(programClass) + programMethod.getDescriptor(programClass) + "]");
            }

            complexEnumMarker.visitProgramClass(programClass);
        }
    }

    // Implementations for ParameterVisitor.

    public void visitParameter(Clazz clazz, Member member, int parameterIndex, int parameterCount, int parameterOffset,
        int parameterSize, String parameterType, Clazz referencedClass) {
        // Check if the parameter is passing a simple enum as a more general
        // type.
        int stackEntryIndex = parameterSize - parameterOffset - 1;
        if (ClassUtil.isInternalClassType(parameterType)
            && !isPoppingExpectedType(invocationOffset, stackEntryIndex, ClassUtil.isInternalArrayType(parameterType)
                ? parameterType : ClassUtil.internalClassNameFromClassType(parameterType))) {
            if (DEBUG) {
                ReferenceValue poppedValue =
                    partialEvaluator.getStackBefore(invocationOffset).getTop(stackEntryIndex).referenceValue();
                if (isSimpleEnumType(poppedValue)) {
                    System.out.println("SimpleEnumUseChecker: [" + poppedValue.getType() + "] "
                        + (member instanceof Field
                            ? ("is stored as more general type [" + parameterType + "] in field [" + clazz.getName()
                                + "." + member.getName(clazz) + "]")
                            : ("is passed as more general argument #" + parameterIndex + " [" + parameterType + "] to ["
                                + clazz.getName() + "." + member.getName(clazz) + "]")));
                }
            }

            // Make sure the popped type is not a simple enum type.
            markPoppedComplexEnumType(invocationOffset, stackEntryIndex);
        }
    }

    // Small utility methods.

    /**
     * Returns whether the specified enum method is supported for simple enums.
     */
    private boolean isSupportedMethod(String name, String type) {
        return name.equals(ClassConstants.METHOD_NAME_ORDINAL) && type.equals(ClassConstants.METHOD_TYPE_ORDINAL) ||

            name.equals(ClassConstants.METHOD_NAME_CLONE) && type.equals(ClassConstants.METHOD_TYPE_CLONE);
    }

    /**
     * Returns whether the specified enum method is unsupported for simple enums.
     */
    private boolean isUnsupportedMethod(String name, String type) {
        return name.equals(ClassConstants.METHOD_NAME_VALUEOF);
    }

    /**
     * Returns whether the specified enum method shall be skipped when analyzing checkcast instructions.
     */
    private boolean isMethodSkippedForCheckcast(String name, String type) {
        return name.equals(ClassConstants.METHOD_NAME_VALUEOF) || name.equals(ClassConstants.METHOD_NAME_VALUES);
    }

    /**
     * Unmarks simple enum classes that are mixed with incompatible reference types in the stack before the given
     * instruction offset.
     */
    private void checkMixedStackEntriesBefore(int offset) {
        TracedStack stackBefore = partialEvaluator.getStackBefore(offset);

        // Check all stack entries.
        int stackSize = stackBefore.size();

        for (int stackEntryIndex = 0; stackEntryIndex < stackSize; stackEntryIndex++) {
            // Check reference entries.
            Value stackEntry = stackBefore.getBottom(stackEntryIndex);
            if (stackEntry.computationalType() == Value.TYPE_REFERENCE) {
                // Check reference entries with multiple producers.
                InstructionOffsetValue producerOffsets =
                    stackBefore.getBottomActualProducerValue(stackEntryIndex).instructionOffsetValue();

                int producerCount = producerOffsets.instructionOffsetCount();
                if (producerCount > 1) {
                    // Is the consumed stack entry not a simple enum?
                    ReferenceValue consumedStackEntry = stackEntry.referenceValue();

                    if (!isSimpleEnumType(consumedStackEntry)) {
                        // Check all producers.
                        for (int producerIndex = 0; producerIndex < producerCount; producerIndex++) {
                            if (!producerOffsets.isExceptionHandler(producerIndex)) {
                                int producerOffset = producerOffsets.instructionOffset(producerIndex);

                                if (DEBUG) {
                                    ReferenceValue producedValue =
                                        partialEvaluator.getStackAfter(producerOffset).getTop(0).referenceValue();
                                    if (isSimpleEnumType(producedValue)) {
                                        System.out.println("SimpleEnumUseChecker: [" + producedValue.getType()
                                            + "] mixed with general type on stack");
                                    }
                                }

                                // Make sure the produced stack entry isn't a
                                // simple enum either.
                                markPushedComplexEnumType(producerOffset);
                            }
                        }
                    }
                }
            }
        }
    }

    /**
     * Unmarks simple enum classes that are mixed with incompatible reference types in the variables before the given
     * instruction offset.
     */
    private void checkMixedVariablesBefore(int offset) {
        TracedVariables variablesBefore = partialEvaluator.getVariablesBefore(offset);

        // Check all variables.
        int variablesSize = variablesBefore.size();

        for (int variableIndex = 0; variableIndex < variablesSize; variableIndex++) {
            // Check reference variables.
            Value variable = variablesBefore.getValue(variableIndex);
            if (variable != null && variable.computationalType() == Value.TYPE_REFERENCE) {
                // Check reference variables with multiple producers.
                InstructionOffsetValue producerOffsets =
                    variablesBefore.getProducerValue(variableIndex).instructionOffsetValue();

                int producerCount = producerOffsets.instructionOffsetCount();
                if (producerCount > 1) {
                    // Is the consumed variable not a simple enum?
                    ReferenceValue consumedVariable = variable.referenceValue();

                    if (!isSimpleEnumType(consumedVariable)) {
                        // Check all producers.
                        for (int producerIndex = 0; producerIndex < producerCount; producerIndex++) {
                            if (!producerOffsets.isMethodParameter(producerIndex)) {
                                int producerOffset = producerOffsets.instructionOffset(producerIndex);

                                if (DEBUG) {
                                    ReferenceValue producedValue = partialEvaluator.getVariablesAfter(producerOffset)
                                        .getValue(variableIndex).referenceValue();
                                    if (isSimpleEnumType(producedValue)) {
                                        System.out.println("SimpleEnumUseChecker: [" + producedValue.getType()
                                            + "] mixed with general type in variables");
                                    }
                                }

                                // Make sure the stored variable entry isn't a
                                // simple enum either.
                                markStoredComplexEnumType(producerOffset, variableIndex);
                            }
                        }
                    }
                }
            }
        }
    }

    /**
     * Returns whether the instruction at the given offset is popping two identical reference types.
     */
    private boolean isPoppingIdenticalTypes(int offset, int stackEntryIndex1, int stackEntryIndex2) {
        TracedStack stackBefore = partialEvaluator.getStackBefore(offset);

        String type1 = stackBefore.getTop(stackEntryIndex1).referenceValue().getType();
        String type2 = stackBefore.getTop(stackEntryIndex2).referenceValue().getType();

        return type1 == null ? type2 == null : type1.equals(type2);
    }

    /**
     * Returns whether the instruction at the given offset is popping exactly the reference type of the specified class
     * constant.
     */
    private boolean isPoppingExpectedType(int offset, Clazz clazz, int constantIndex) {
        return isPoppingExpectedType(offset, 0, clazz, constantIndex);
    }

    /**
     * Returns whether the instruction at the given offset is popping exactly the reference type of the specified class
     * constant.
     */
    private boolean isPoppingExpectedType(int offset, int stackEntryIndex, Clazz clazz, int constantIndex) {
        return isPoppingExpectedType(offset, stackEntryIndex, clazz.getClassName(constantIndex));
    }

    /**
     * Returns whether the instruction at the given offset is popping exactly the given reference type.
     */
    private boolean isPoppingExpectedType(int offset, int stackEntryIndex, String expectedType) {
        TracedStack stackBefore = partialEvaluator.getStackBefore(offset);

        String poppedType = stackBefore.getTop(stackEntryIndex).referenceValue().getType();

        return expectedType.equals(poppedType);
    }

    /**
     * Returns whether the given method is returning a simple enum type. This includes simple enum arrays.
     */
    private boolean isReturningSimpleEnumType(Clazz clazz, Method method) {
        String descriptor = method.getDescriptor(clazz);
        String returnType = ClassUtil.internalMethodReturnType(descriptor);

        if (ClassUtil.isInternalClassType(returnType)) {
            Clazz[] referencedClasses = ((ProgramMethod)method).referencedClasses;

            if (referencedClasses != null) {
                Clazz referencedClass = referencedClasses[referencedClasses.length - 1];

                return isSimpleEnum(referencedClass);
            }
        }

        return false;
    }

    /**
     * Returns whether the instruction at the given offset is popping a type with a simple enum class. This includes
     * simple enum arrays.
     */
    private boolean isPoppingSimpleEnumType(int offset) {
        return isPoppingSimpleEnumType(offset, 0);
    }

    /**
     * Returns whether the instruction at the given offset is popping a type with a simple enum class. This includes
     * simple enum arrays.
     */
    private boolean isPoppingSimpleEnumType(int offset, int stackEntryIndex) {
        ReferenceValue referenceValue =
            partialEvaluator.getStackBefore(offset).getTop(stackEntryIndex).referenceValue();

        return isSimpleEnumType(referenceValue);
    }

    /**
     * Returns whether the given value is a simple enum type. This includes simple enum arrays.
     */
    private boolean isSimpleEnumType(ReferenceValue referenceValue) {
        return isSimpleEnum(referenceValue.getReferencedClass());
    }

    /**
     * Returns whether the given class is not null and a simple enum class.
     */
    private boolean isSimpleEnum(Clazz clazz) {
        return clazz != null && SimpleEnumMarker.isSimpleEnum(clazz);
    }

    /**
     * Marks the enum class of the popped type as complex.
     */
    private void markConstantComplexEnumType(Clazz clazz, int constantIndex) {
        clazz.constantPoolEntryAccept(constantIndex, referencedComplexEnumMarker);
    }

    /**
     * Marks the enum class of the popped type as complex.
     */
    private void markPoppedComplexEnumType(int offset) {
        markPoppedComplexEnumType(offset, 0);
    }

    /**
     * Marks the enum class of the specified popped type as complex.
     */
    private void markPoppedComplexEnumType(int offset, int stackEntryIndex) {
        ReferenceValue referenceValue =
            partialEvaluator.getStackBefore(offset).getTop(stackEntryIndex).referenceValue();

        markComplexEnumType(referenceValue);
    }

    /**
     * Marks the enum class of the specified pushed type as complex.
     */
    private void markPushedComplexEnumType(int offset) {
        ReferenceValue referenceValue = partialEvaluator.getStackAfter(offset).getTop(0).referenceValue();

        markComplexEnumType(referenceValue);
    }

    /**
     * Marks the enum class of the specified stored type as complex.
     */
    private void markStoredComplexEnumType(int offset, int variableIndex) {
        ReferenceValue referenceValue =
            partialEvaluator.getVariablesAfter(offset).getValue(variableIndex).referenceValue();

        markComplexEnumType(referenceValue);
    }

    /**
     * Marks the enum class of the specified value as complex.
     */
    private void markComplexEnumType(ReferenceValue referenceValue) {
        Clazz clazz = referenceValue.getReferencedClass();
        if (clazz != null) {
            clazz.accept(complexEnumMarker);
        }
    }
}
